CO-Horts

CO-Horts

Thursday, April 18, 2013

"Promise America" to Not Move Firewood!

Alexis Alvey, Horticulture Agent, CSU Denver Extension

What do baseball bats, bugs, and ash trees all have in common?
(And no, this is not some lame, bar room joke.) Well, they are all part
of the "Promise America" campaign initiated by the US Department of
Agriculture. This campaign has been launched to educate everyday
homeowners and gardening enthusiasts alike about the invasive insect pest
called the Emerald Ash Borer (Agrilus planipennis) which is killing
literally millions of ash trees across America. There are a handful of
different species of ash trees that are native to the Midwest and the East
Coast that are commonly planted as great urban street trees throughout the US,
including Denver. Wood from ash trees
has traditionally been used to make baseball bats. Unfortunately, all of
our native ash, including White Ash (Fraxinus americana) and Green Ash (Fraxinus
pennsylvanica), which are the two species planted in horticulture, are
completely at the mercy of Emerald Ash Borer. This tree-killing
beetle was first identified in the US in 2002 near Detroit, Michigan and is
native to eastern Russia, northern China, Japan, and Korea. No one knows
for sure how or when it got here, but most likely in the 1990s it came to the
US in ash wood used for stabilizing cargo in ships or for packing or crating
heavy consumer products. It has now spread into seventeen additional
states and two Canadian provinces and continues expanding its range. Its
spread has been accelerated by the movement of infested firewood. Last year it was discovered in Kansas for the
first time, and people are worried that it will soon be in Colorado. Denver
Parks & Recreation’s Forestry Division will begin monitoring for Emerald
Ash Borer for the first time this season.

The Emerald Ash
Borer is actually a relatively pretty insect (I say relative, because in my
opinion all insects are kind-of gross.) The adult beetles are a bright,
metallic green, a half-inch long, and have a flattened back. But the problem is
not the adult beetles, it is their larvae. The larvae are a type of
flatheaded borer. (By the way, “You are
such a flathead!!” makes for a great insult!)
Larvae hatch from eggs laid within bark crevices and under bark scales
in the spring. They chew through the
outer bark of the tree and into the cambium where they feed in the phloem
interrupting the flow of nutrients within the tree, ultimately girdling
it.

Signs and symptoms of Emerald Ash Borer infestation are yellowing leaves
on branches and then dieback generally in the top of the tree canopy
first. Sprouting from the base of the
trunk can also occur. If you are lucky
and look very very carefully, you may see small holes in the trunk that are 1/8”
in diameter and that are D-shaped.
Complete defoliation and tree death typically occurs within 2-3
years.

Photo: Green Ash dead due to Emerald Ash Borer

(David Cappaert, Michigan State University, Bugwood.org)

Unfortunately there is no simple cure for Emerald Ash Borer. This little beetle has had an enormous
economic and ecological impact. The
devastation of the insect is remarkable - over 53 million ash trees have died
or are dying from the borer and all of North America's 7 billion ash trees are
at risk. It is estimated that up to $26 billion has been lost due to the
borer in just four Midwestern states.
This took into account the cost of lost tree value, tree removal, and
tree replacement.

Invasive pests have been incredibly problematic for our urban
trees and native forests for the past century.
From Dutch Elm Disease to Chestnut Blight to Asian Longhorn Beetle,
invasive insects and disease have changed the composition and ecological
functioning of our forests as well as their look and feel. So please, “Promise America” that you will
not move firewood; that you will burn firewood where you buy it; and that you will
plant a diverse selection of trees and not all the same species. Oh, and that old
wooden baseball bat of yours may be more valuable than you think!